Axial positioner and seal for cooled rotor blade

ABSTRACT

An axial positioning and sealing means for axially positioning turbine blades with respect to a rotor disc and for sealing the downstream side of cooling fluid flow passageways below the root portions of the blades is disclosed. The periphery of the rotor disc is provided with axial channels for receiving the root portions of turbine blades having radial cooling bores extending from the root portions through the tips of the blades. The channels are formed to provide an axially extending passageway communicating with the cooling bores whereby a cooling fluid flows through the passageway and into the bores to cool the plates. Sideplates means are provided for retaining the blades to the rotor disc. Pads or protrusions are provided on each steeple of the rotor disc, with the pads being positioned and shaped such that the side faces of two adjacent pads define a radially extending, radially outwardly tapering channel over each of the passageways. Each positioning and sealing plate has tapered sides complementary in shape to the tapered channel whereby when said rotor disc is rotated at high speeds, the centrifugal force acting on said plate will urge the plate radially outwardly of the rotor disc to thereby wedge the plate against the pad and the root portion of the turbine blades. Locking means are provided for securing each plate against unlimited radial inward movement with respect to the rotor disc.

United States Patent 1 Hugoson et al. 51 Apr. 17, 1973 [5 AXIALPOSITIONER AND SEAL FOR [57] ABSTRACT COOLED ROTOR BLADE An axialpositioning and sealing means for axially [75] Inventors: Birger O.Hugoson, Wallingford, positioning turbine blades with respect to a rotordisc Pa.; Norbert Vettel, Buergel, Gerand for sealing the downstreamside of cooling fluid many flow passageways below the root portions ofthe blades is disclosed. The periphe of the rotor disc is [73] Asslgnee'Westmghouse Electnc Corporation provided with axial channels f rreceiving the root Pmsburgh portions of turbine blades having radialcooling bores [22] Filed: Aug. 27, 1971 extending from the root portionsthrough the tips of the blades. The channels are formed to provide anaxi- [211 Appl' 175590 ally extending passageway communicating with thecooling bores whereby a cooling fluid flows through 52 US. Cl. ..4l6/95the p g y and into the bores to cool the plates. [5 1 F02d 5/08Sideplates means are provided for retaining the blades [58] Field ofSearch .416/92, 95, 96, 97, to the rotor disc- 416/220, 221 Pads orprotrusions are provided on each steeple of the rotor disc, with thepads being positioned and [56] References C'ted shaped such that theside faces of two adjacent pads UNITED STATES PATENTS define a radiallyextending, radially outwardly tapering channel over each of thepassageways. Each position- 3,644,058 5/1970 Bamabel et al. ..416/95 ingand sealing plate has tapered sides complementary 3,572,966 1971 d n el..4l6/95 in shape to the tapered channel whereby when said 52 /l rlstr tal.. rotor disc is rotated at high speeds, the centrifugal 3,043,5627/1962 Nest "416/221 force acting on said plate will urge the plateradially 2,801,074 7/1957 Brown i i ..4l6/221 outwardly f h rotor discto thereby wedge the plate 3,501,249 3/1970 Scalzo et al. ..4l6/22OPrimary Examiner-Everette A. Powell, Jr. Assistant Examiner-Robert E.Garrett Attorney-A. T. Stratton et al.

against the pad and the root portion of the turbine blades. Lockingmeans are provided for securing each plate against unlimited radialinward movement with respect to the rotor disc.

7 Claims, 5 Drawing Figures PATENTEUAPR 1 H915 3'. 728,042

SHEET 1 OF 3 W PATENTED APR] 7 I973 SHEET 2 [1F 3 PATENTEB APR 1 7 I973SHEET 3 OF 3 AXIAL POSITIONER AND SEAL FOR COOLED ROTOR BLADE BACKGROUNDOF THE INVENTION The present invention relates generally to turbinerotors and particularly to a structure for axially positioning andsealing fluid cooled turbine blades within the periphery of a bladesupporting disc.

It is a well-known practice to use sideplates to secure turbine rotorblades of the side entry type in a rotor disc of a turbine. In oneturbine blade and rotor disc arrangement where the blades are cooled bycooling fluid flowing through radial bores in the blades, the blades areabutted against a ledge of an upstream sideplate mounted on the rotordisc and individual sideplates are disposed in grooves formed on thedownstream side of the blades for securing the blades to the rotor disc.The sideplates are usually positioned at the radially outer region ofthe root portions of the turbine blades. An axial positioning andsealing plate is disposed at the radial inner region of the rootportions of each blade for axially positioning the blade with respect tothe rotor disc and for sealing an axial passageway radially inwardly ofthe bottom of the root portion. The axial passageway communicates withthe radial bores through the turbine blades whereby a cooling fluidflows through the passageway and into the bores to cool the blades.

One type of axial positioning and sealing plte structure includes asealing plate fitted into grooves formed at the radial inner region ofthe blade root portion and an opposing rotor disc section. A lockingplate flts on the downstream side of the sealing plate, with both theplates being secured in place by a lock bolt extending through the rotordisc and the locking plate. The bolts are locking in place by use oflockwashers or lockwires. Although the double plate type of structureprovided adequate axial positioning of the blades as well as sealing forthe cooling fluid passageway, the structure is somewhat complex since itrequires four parts as well as the machining of circumferential grooveson both the blade root portions and rotor disc. In addition, the doubleplate structure is undesirable in that it is not capable of simpleassembly and disassembly between the turbine blades and the rotor discs.The double plate structure requires sequential installation within thegrooves, and when one blade needs to be removed from the rotor disc allof the plates to one side of that blade must be removed first. Thisrequires a time consuming and expensive procedure.

The known axial positioning and sealing plate structures are alsosubject to buckling due to the stress they are placed under as a resultof the tangential forces on the plates during rotation of the rotordisc. In order to avoid such buckling the plates are thick and strongenough to resist the buckling stresses. By so designing the plates theweight and costs of the sideplates increase.

BRIEF SUMMARY The present invention overcomes the undesirable featuresnoted above with respect to the known axial positioning and sealingplate structures. Thus, the present invention provides a simple platestructure which is easy to assemble and disassemble and may be removedand replaced without moving adjoining plates,

is shaped to provide effective axial positioning and sealing of theturbine blades with respect to the rotor disc, and is shaped andarranged for diminishing the tendency to buckle, thereby permitting athinner plate construction. The noted advantages result from a structurewhich includes pad or protrusion means on the downstream surface of eachsteeple of a rotor disc having channels provided in the peripherythereof for receiving the root portions of turbine blades, which padmeans is positioned and shaped such that the side faces of two adjacentpad means define a radially extending radially outwardly taperingchannel. Each of the axial channels in the rotor disc are provided withaxial passageways for conducting a flow of cooling fluid. Thepassageways communicate with radially extending cooling bores in theturbine blades so that cooling fluid will flow from the passagewaysthrough the cooling bores to thereby cool the turbine blades. The radialchannels defined by the pad means are arranged over each of the axialpassageways. Axial positioning and sealing plates are provided with eachplate being received in one of the radial channels and having taperingsides complementary in shape to the tapering sides of the radialchannel, whereby when the rotor disc is rotated at high speeds thecentrifugal force acting on the plate will urge the plate radiallyoutwardly to thereby wedge the plate against the pad means and the rootportions of the turbine blades. Locking means, such as lock wiresthrough the radially outer portions of the blades, are provided forsecuring the plates against unlimited radial inward movement withrespect to the rotor disc. In the preferred form, the radial channel andplate are provided with complementary bevelling on the sides thereof toenhance the wedging effect due to the radially outward movement of theplates during high speed rotation of the rotor disc. Also, in thepreferred form the bevelling of the radial channel and plate are shapedso that the tangential stress on the plates are borne by the axialdownstream portion of the sides of the plates thereby reducing thetendency of the plates to buckle.

THE DRAWINGS The present invention, along with its detailsc andadvantages, will be better understood from the following detaileddescription taken in connection with the accompanying drawings in which:

FIG. I is a longitudinal section of a radial portion of an axial flowturbine showing a rotor disc and axial positioning and seal platestructure constructed in accordance with the principles of the presentinvention;

FIG. 2 is a perspective view of the root and blade extenion portion ofturbine blades and portion of a rotor disc showing the axial positioningand seal plate structure of the present invention arranged to seal thecooling fluid passageway below the blade root portions;

FIG. 3 is a sectional view looking along the line III- III of FIG. 2showing the angular relationship between the side facesof the axialpositioning and seal palte and the pads on the steeples of the rotordisc;

FIG. 4 is a perspective view similar to that of FIG. 2 showing anotherconfiguration of axial positioning and seal plates, and pads of thepresent invention, and

FIG. 5 is a perspective view of an axial positioning and seal plate asshown in FIG. 4 showing more clearly the spherical contour of the sideedges thereof.

PREFERRED EMBODIMENTS Referring now to the drawings, FIG. 1 shows aportion of a rotor of an axial flow turbine in longitudinal section. Therotor 10 may comprise an aggregate of rotor discs, only one of which 12is shown, secured together by circumferentially disposed tie or staybolts extending through the discs.

The rotor disc 12 is a first stage disc and supports turbine blades 14extending radially outwardly therefrom, the blades being disposedbetween axially spaced inwardly extending fixed stator or nozzle blades16 and 18. The turbine blades 14 are provided with root portions 20 ofthe side entry type which may be of the serrated of fir tree" type fordisposition in axially extending serrated slots 22 formed in the outerperiphery of rotor disc 12, as shown in FIG. 2. The lower or radialinward section of the slots 22 are formed and sized to provide aclearance with the lower end of root portion 20, which clearance servesas a passageway 24 for directing cooling fluid to the root portion andthe rotor disc as shown. The passageway 24 communicates with radialcooling holes or bores 26 extending from the bottom of the root portion20 of the blades 14 through the tips of the airfoil portion thereof. Theturbine blades 14 are further provided with the usual platform and ablade extension 30 between the platform and the root portion 20.

The rotor disc 12 is also provided with a passageway 32 at the upstreamside thereof, and formed by an upstream sideplate 34 secured to theupstream face of the main body portion of the rotor disc bycircumferentially disposed tie bolts 36 extending through the upstreamsideplate and rotor disc, only one tie bolt being shown in FIG. 1.Passageway 32 is arranged to communicate with passageway 24 in themanner shown. An air separator plate 38 is secured to upstream sideplate34 in any well-known manner, with the separator plate and upsteamsideplate shaped to define a passageway 40 communicating with passageway32. Passageway 40 is connected with a source of cooling fluid, notshown, whereby the cooling fluid will flow through theintercommunicating passageways 40, 32, and 24 and through the coolingbores 26 for cooling the turbine blades 14.

The upstream sideplate34 is formed with a radial outer, annular ledge 44arranged to extend from the top of passageway 24 to slightly above thetop of the steeple 46 of the rotor disc 12. The ledge 44 serves as theupstream stop for the turbine blades 14 when they are positioned in theslots 22 of the rotor disc 12. The ledge 44 is also designed to provideclose abutting con tact with the steeples 46 and root portions 20 of theturbine blades 14 to thereby seal the root portions from the hot motivefluid at the upstream side of the turbine blades. The turbine blades 14are secured to rotor disc 12 by means of sideplates 48 fitted intogrooves 49 provided in the downstream end of the platforms 28 of turbineblades and arranged to snuggly abut blade extensions 30 of the turbineblades and the adjacent steeples 46 of the rotor disc 12.

The downstream end of passageway 24 is sealed by axial positioning andsealing plates 50 which also serve to axially position the turbineblades 14 within slots 22 of rotor disc 12. Each plate 50 is sized andshaped to fit snugly between two adjacent steeples 46 to overlap thedownstream end of passageway 24. As shown in FIG. 2,

a protrusion or pad 52 having a radially inwardly taperingfrustopyramidal shape, is provided on the lower section of each steeple46 adjacent the passageways 24. A pair of adjacent pads 52, thus, definea radially outwardly tapering channel 54 which extends over eachpassageway 24. The side edges 56 of the pads 52 are provided with abevelling which tapers outwardly as viewed in FIG. 2 or, stateddifferently, taper in an axially convergent direction relative to thedirection of motive fluid flow. Thus, looking downstream of rotor disc12, the side edges 56 of a pair of adjacent pads 52 taper or convergetowards a line parallel to the axis of rotor disc 12 and passing midwaybetween the channel 54 defined between the pads.

Each axial positioning and sealing plate 50 has a generallyfrusto-pyramidal shape and is provided with side edges 60 havingbevelling complementary in pitch to that of the side edges 56 of pads52. The taper of each plate 50 complements that of a channel 54 definedbetween a pair of adjacent pads 52. Thus, when a plate 50 is fitted in achannel 54 and urged in a radially outward direction the upstream faceof the plate will cover the dnstream end of passageway 24 and willsnugly engage the adjoining surface portions of the root portion 20,rotor disc 12 body, and steeples 46 to thereby seal the downstream endof passageway 24.

When the rotor disc 12 is rotated at high speeds the centrifugal forceacting 'on the axial positioning and sealing plates 50 will cause theplates to move radially outwardly in channels 54. The bevelling betweenthe engaging side edges 56 and 60 of the pads 52 and plates 50,respectively, will result in the plates wedging between the pads in amanner to urge the turbine blades 14 into axial position in the slots 22of rotor disc 12, and also to tightly abut the surfaces around thedownstream ends of the passageways 24 to provide effective seals for thepassageways 24.

Locking means are provided for securing the plates 50 within thechannels 54 against radial inward movement when the rotor disc 12 is atrest or rotating at low speeds. A retaining wire 64 is fitted'incircumferentially extending openings in the radial outward portion ofthe plates 50. the wire 64 may extend between two or more sequentiallyspaced plates 50 and the free ends turned radially outwardly in themanner shown in FIG. 2. The retaining wires 64 are located such thatthey will engage the upper or radially outward surfaces of the pads 52and thery prevent unlimited radial inward move ment of the plates 50.

The taper angle of the channel 54 and the plates 50, should be selectedto as to avoid excessive tangential forces acting on the plates 50 whileat the same time the tapers should be such as to provide a good wedgingaction between the plates 50 and pads 52 to thereby give good axialpositioning for the turbine blades 14 and effective sealing of thedownstream end of the passageways 24. Tangential forces acting on theplates 50 tend to buckle the plates and therefore such forces should beminimized. The maximum tangential force wil occur where there would beno taper in a channel 54. Making the taper angle of a channel 54 toolarge would diminish the wedging effect between the plates 50 and thepads 52. Thus, a suitable taper angle of the channels 54 and plates 50should be selected to achieve the desired minimization of tangentialforces acting on the plates while providing the desired wedging effectbetween the plates 50 and pads 52. Those skilled in the art wouldreadily recognize how to. calculate the desired taper angle of thechannels 54 and plates 50. The tangential forces, which depend on speedand radius of rotor disc 12, would be one factor which would determinethe taper angle.

As shown in FIG. 3, the bevel angle of the side edges of plates 50 isless than that of the side edges 56 of pads 52 whereby when the plates50 are positioned between the pads 52, the downstream section of theside edges 60 of plates 50 will engage the downstream section of theside edges 56 of pads in the manner shown in FIG. 3. This arrangement ofthe respective side edges 56 and 60 will reduce the effect of tangentialforces acting on the plates 50 since the stress on the plates 50 will beborne by the downstream section of the side edges of the plates. Withthe side edges of the plates 50 and pads 52 being flush with each other,the stress on the plates 50 due to the tangential forces would more thanlikely be borne by the upstream section of the side edges 60 of theplates 50 with the tendency of the plates 50 to buckle being greaterthan when the stresses are borne at the upstream section of the sideedges. Thus, the relationship between the side edges of the plates 50and pads 52 just described and shown in FIG. 3, reduce the tendency ofthe plaees 50 to buckle.

FIGS. 4 and 5 show another embodiment of the present invention. Theaxial positioning and retaining plate shown is generally circular ordisc shaped and has a spherically shaped edge 72. Pads 74 are providedon the steeples 46' of the rotor disc 12 with the pads 74 having agenerally frusto-pyramdal shape tapering radially inwardly whereby aradially outwardly tapering channel is defined between each pair ofadjacent pads. The side edges 76 of the pads 74 are generallyspherically shaped complementary to the shape of the edge of plates 70.The configuration of the plates 70 and pads 74 wlll result in a wedgingof the plates with respect to the pads with the consequent positiveeffect on the axial positioning of the turbine blades 14' within 22' ofrotor disc 12 and the sealing of the downstream end of the passageways24'. The same considerations with regard to the taper of the channelsbetween the pads 74 and the shape of the plates 70 for purposes ofminimizing tangential forces and maintaining effecting wedging, would bemade in this embodiment as would be made with the earlier describedembodiment.

Locking means are provided for securing the plates 70 against unlimitedradial inward movement with respect to the rotor disc 12'. Acircumferential groove 80 is provided on the downstream face of therotor disc 12 and is sized and located to receive the free ends of aretaining wire 82 fitted through a circumferentially extending openingprovided through the radially inward or bottom section of plate 70.Thus, when rotor disc 12 is at a standstill or rotating at low speeds,the retaining wires 82 cooperating with groove 80 will secure the plates70 between the pads 72.

Since the axial positioning and sealing plates 50 and 70 are not readilysusceptible to buckling, thinner material may be used as compared withthe plate structures used heretofore, with attendant savings in weightand cost. Also, the plates 50 and 70 may be assembled and disassembledindividually without moving adjacent plates. These, and other positiveresults are realized, by this invention while the invention at the sametime provides effective axial positioning of the turbine blades in therotor disc and effective sealing of the downstream end of the bladecooling fluid axial flow passageway in the rotor disc.

Though the invention has been shown and described in preferred forms, itwill be obvious to those skilled in the art that it is not so limited,but is susceptible of changes without departing. from the spirit andscope thereof. For example, the locking means for securing the axialpositioning and sealing plates, rather than being retaining wires, couldbe lock bolts extending through the plates partially into the axialpassageway below the root portion of the turbine blades.

We claim:

1. In a rotor for an axial flow fluid machine, the rotor comprng atleast one rotor disc with slots provided in the periphery thereof forreceiving the root portions of rotor blades said slots defining steeplestherebetween, said rotor blades having radial cooling bores extendingfrom the root portions through the tips of the blades, passagewaysextending axially of the root portions, said passageways communicatingwith the cooling bores and being capable of conducting a flow of coolingfluid therethrough, and sideplate means associated with said blades forsecuring said blades to said rotor disc, the improvement comprising:

an axial positioning and sealing plate associated with each blade forpositioning the blades axially with respect to said rotor disc and forsealing the downstream side of each of said passageways;

pad means on each steeple of said rotor disc positioned and shaped suchthat the side faces of two adjacent pad means define a radiallyoutwardly extending, radially outwardly converging tapering channel overeach of said passageways;

said plate being received in said channel and having tapering sidscomplementary in shape to said tapering channel whereby when said rotordisc is rotated at high speeds the centrifugal force acting on saidplate will urge said plate radially outwardly of said rotor disc tothereby wedge said plate against said pad means and the root portions ofthe turbine blades; and

locking means for securing said plate against unlimited radial inwardmovement with respect to said rotor disc.

2. The structure recited in claim 1 in which the side faces of said padmeans are bevelled in an axially convergent direction relative to thedirection of fluid flow, and said plates are provided with bevelled sidesurfaces complementary in shape to the beveliing of said side faces ofsaid pad means.

3. The structure as recited in claim 1 in which the side faces of saidpad means and the sides of said plates are generally flat planarsurfaces.

4. The structure as recited in claim 1 in which said pates are generallycircular in shape with the sides thereof being generally sphericallyshaped, and the side faces of said pad means are generally sphericallyshaped complementary to the shape of said sides of said plates.

5. The structure as recited in claim 1 in which said locklng means is anelongated retaining member extending through a portion of each of saidplates disposed radially outwardly relative to said pad means andarranged to engage said pad means to secure said plates.

6. The structure as recited in claim 1 in which said locking meansincludes a circumferential groove provided in said rotor disc radiallyinwardly of said pad means, and an elongatd retaining member extendingthrough a portion of each of said plates disposed radially inwardlyrelative to said pad means and arranged to fit within saidcircumferential groove to secure said plates.

7. The structure as set forth in claim 2 in which the side faces of saidpad means and the sides of said plates are generally flat planarsurfaces, and the angle of the bevelling of said side faces of said padmeans is greater relative to the axis of said rotor disc than the angleof the bevelling of the side surfaces of said plates, the difference ofthe angles being such that the downstream portions of the respectiveside surfaces of said plates and pad means engage each other while aclearance exists between the upstream of the respective side surfaces. 7

1. In a rotor for an axial flow fluid machine, the rotor comprising atleast one rotor disc with slots Provided in the periphery thereof forreceiving the root portions of rotor blades, said slots definingsteeples therebetween, said rotor blades having radial cooling boresextending from the root portions through the tips of the blades,passageways extending axially of the root portions, said passagewayscommunicating with the cooling bores and being capable of conducting aflow of cooling fluid therethrough, and sideplate means associated withsaid blades for securing said blades to said rotor disc, the improvementcomprising: an axial positioning and sealing plate associated with eachblade for positioning the blades axially with respect to said rotor discand for sealing the downstream side of each of said passageways; padmeans on each steeple of said rotor disc positioned and shaped such thatthe side faces of two adjacent pad means define a radially outwardlyextending, radially outwardly converging tapering channel over each ofsaid passageways; said plate being received in said channel and havingtapering sides complementary in shape to said tapering channel wherebywhen said rotor disc is rotated at high speeds the centrifugal forceacting on said plate will urge said plate radially outwardly of saidrotor disc to thereby wedge said plate against said pad means and theroot portions of the turbine blades; and locking means for securing saidplate against unlimited radial inward movement with respect to saidrotor disc.
 2. The structure recited in claim 1 in which the side facesof said pad means are bevelled in an axially convergent directionrelative to the direction of fluid flow, and said plates are providedwith bevelled side surfaces complementary in shape to the bevelling ofsaid side faces of said pad means.
 3. The structure as recited in claim1 in which the side faces of said pad means and the sides of said platesare generally flat planar surfaces.
 4. The structure as recited in claim1 in which said plates are generally circular in shape with the sidesthereof being generally spherically shaped, and the side faces of saidpad means are generally spherically shaped complementary to the shape ofsaid sides of said plates.
 5. The structure as recited in claim 1 inwhich said lock1ng means is an elongated retaining member extendingthrough a portion of each of said plates disposed radially outwardlyrelative to said pad means and arranged to engage said pad means tosecure said plates.
 6. The structure as recited in claim 1 in which saidlocking means includes a circumferential groove provided in said rotordisc radially inwardly of said pad means, and an elongatd retainingmember extending through a portion of each of said plates disposedradially inwardly relative to said pad means and arranged to fit withinsaid circumferential groove to secure said plates.
 7. The structure asset forth in claim 2 in which the side faces of said pad means and thesides of said plates are generally flat planar surfaces, and the angleof the bevelling of said side faces of said pad means is greaterrelative to the axis of said rotor disc than the angle of the bevellingof the side surfaces of said plates, the difference of the angles beingsuch that the downstream portions of the respective side surfaces ofsaid plates and pad means engage each other while a clearance existsbetween the upstream of the respective side surfaces.